The present invention relates to a flame-retardant polycarbonate resin composition and to electrical and electronic components of housings of office automation equipment, housings of electrical and electronic appliances and battery packs as made by molding the composition. More precisely, it relates to a flame-retardant, non-bromine polycarbonate resin composition having good flame retardancy, good mechanical properties including impact resistance, good flowability and good moldability, and to housings of office automation equipment, housings of electrical and electronic appliances and battery packs as made by molding the composition.
As having good mechanical properties (especially high impact resistance), good electric properties, and good transparency, polycarbonate resins are widely used as engineering plastics in various fields of office automation equipment, electrical and electronic appliances, building materials, etc.
Among various thermoplastic resins, polycarbonate resins have a high oxygen index and are generally self-extinguishable. However, especially in the fields of office automation equipment and electrical and electronic appliances, concretely for applications to housings of office automation equipment, to housings of electrical and electronic instruments such as notebook-type personal computers and others, and to battery packs, resin compositions with much more improved flame retardancy are desired to satisfy the requirement for safety operation of those equipment and appliances.
For making resins have flame retardancy, heretofore, flame retardants comprising a bromine compound have been used. One problem with resin compositions that comprise such a bromine-containing flame retardant is that molds used for repeatedly molding the resin compositions are rusted and that the resin compositions being molded are yellowed while in molds. Another problem is that the resin compositions being molded release corrosive gases that may pollute the environment. In that situation, non-bromine flame retardants are being much desired for resin compositions.
On the other hand, office automation equipment and electrical and electronic appliances, concretely, their housings and battery packs are required to have much improved impact resistance. In order to improve the impact resistance of such equipment and appliances, concretely their components, one popular means that has heretofore been generally employed is to add rubbery improvers to polycarbonate resins and to mold the resulting resin compositions. However, this is problematic in that the resin compositions to which is added a large amount of such an impact resistance improver could not have good flame retardancy. For their applications, in particular, battery packs are used for mobile communication appliances such as portable telephones and others or for portable terminals such as notebook-type personal computers and others, and are therefore required to be lightweight and thin-walled. Accordingly, the materials for such battery packs are required to have good moldability and flowability.
Various techniques for those requirements have heretofore been proposed, for example, in JP-A 07-173401, 08-259792, 08-120169, 07-304943, 08-239565, etc. The compositions proposed therein could have flame retardancy in some degree, but are still problematic in that they contain bromine-containing flame retardants, or if not containing bromine-containing flame retardants, their mechanical properties such as impact resistance and also their moldability and flowability are poor.
The object of the invention is to provide a polycarbonate resin composition having improved mechanical properties such as impact resistance, having good moldability and flowability and having good flame retardancy even though not containing a bromine compound, and to provide housings of office automation equipment, housings of electrical and electronic appliances and also battery packs as made by molding the composition.
Given that situation, we, the present inventors have assiduously studied, and, as a result, have found that the object can be attained by adding a composite rubbery graft copolymer to a polycarbonate resin, preferably by adding a specific composite rubbery graft copolymer, a halogen-free phosphoric ester and a polytetrafluoroethylene thereto in a specific ratio of the composite rubbery graft copolymer to the halogen-free phosphoric ester.
The invention has been completed on the basis of these findings.
Specifically, the invention provides a polycarbonate resin composition, and housings of office automation equipment, housings of electrical and electronic appliances, and battery packs as made by molding the composition, which are as follows:
(1) A flame-retardant polycarbonate resin composition comprising (A) a polycarbonate resin and (B) a composite rubbery graft copolymer in a ratio by weight, (A):(B), falling between 99:1 and 90:10, and containing, relative to 100 parts by weight of the sum total of the component (A) and the component (B), (C) from 0.3 to 1.2 Darts by weight. in terms of phosphorus. of a halogen-free phosphoric ester, and (D) from 0.01 to 1.0 part by weight of a polytetrafluoroethylene, in which the ratio by weight of the amount of the composite rubbery graft copolymer (B) to the phosphorus content of the halogen-free phosphoric ester (C) falls between 2 and 15.
(2) The flame-retardant polycarbonate resin composition of (1), wherein the composite rubbery graft copolymer (B) is prepared by grafting a composite rubber, which has a structure composed of from 1 to 99% by weight of a polyorganosiloxane rubber component and from 1 to 99% by weight of a polyalkyl acrylate rubber components, the two components being so intertwisted with each other as not to separate from each other, and has a mean particle diameter of from 0.01 xcexcm to 0.6 xcexcm, with one or more vinyl monomers.
(3) Electrical and electronic components as made by molding the flame-retardant polycarbonate resin composition of (1) or (2).
(4) Housings of office automation equipment, or housings of electrical and electronic appliances, as made by molding the flame-retardant polycarbonate resin composition of (1) or (2).
(5) Battery packs as made by molding the flame-retardant polycarbonate resin composition of (1) or (2).
The invention is described in detail hereinunder.
1. Flame-Retardant Polycarbonate Resin Composition
(1) Description of Constituent Components
[i] Polycarbonate Resin (Component (A))
In the flame-retardant polycarbonate resin composition of the invention, the polycarbonate resin for the component (A) may be any and every one that may be prepared in any ordinary method of, for example, reacting a diphenol with a polycarbonate precursor such as phosgene, carbonate compounds, etc. Concretely, it includes polycarbonate resins as prepared through reaction of a diphenol with a carbonate precursor such as phosgene or transesterification of a diphenol with a carbonate precursor such as diphenyl carbonate, in a solvent of methylene chloride or the like in the presence of a known acid acceptor and a known molecular weight-controlling agent, to which is optionally added a branching agent.
For the reaction, various diphenols are employable. Especially preferred is 2,2-bis (4-hydroxyphenyl)propane (this is generally referred to as bisphenol A). As other bisphenols employable herein in addition to bisphenol A, mentioned are bis (hydroxyaryl) alkanes such as bis (4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 2,2-bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-hydroxy-1-methylphenyl)propane, bis(4-hydroxyphenyl)naphthylmethane, 1,1-bis(4-hydroxy-t-butylphenyl)propane, 2,2-bis(4-hydroxy-3,5-tetramethylphenyl)propane, etc.; bis(hydroxyaryl)cycloalkanes such as 1,1-bis (4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,5,5-trimethylcyclohexane, etc.; dihydroxyaryl ethers such as 4,4xe2x80x2-dihydroxyphenyl ether, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-dimethylphenyl ether, etc.; dihydroxydiaryl sulfides such as 4,4xe2x80x2-dihydroxydiphenyl sulfide, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-dimethyldiphenyl sulfide, etc.; dihydroxydiaryl sulfoxides such as 4,4xe2x80x2-dihydroxydiphenyl sulfoxide, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-dimethyldiphenyl sulfoxide, etc.; dihydroxydiaryl sulfones such as 4,4xe2x80x2-dihydroxydiphenyl sulfone, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-dimethyldiphenyl sulfone, etc.; dihydroxydiphenyls such as 4,4xe2x80x2-dihydroxydiphenyl, etc. One or more of these diphenols may be used either singly or as combined.
The carbonate compound includes, for example, diaryl carbonates such as diphenyl carbonate, etc.; dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, etc.
As the molecular weight-controlling agent, herein employable is any and every one that may be used in polymerization to give polycarbonates. Concretely mentioned are monophenols which include, for example, phenol, o-n-butylphenol, m-n-butylphenol, p-n-butylphenol, o-isobutylphenol, m-isobutylphenol, p-isobutylphenol, o-t-butylphenol, m-t-butylphenol, p-t-butylphenol, o-n-pentylphenol, m-n-pentylphenol, p-n-pentylphenol, o-n-hexylphenol, m-n-hexylphenol, p-n-hexylphenol, p-t-octylphenol, o-cyclohexylphenol, m-cyclohexylphenol, p-cyclohexylphenol, o-phenylphenol, m-phenylphenol, p-phenylphenol, o-n-nonylphenol, m-nonylphenol, p-n-nonylphenol, o-cumylphenol, m-cumylphenol, p-cumylphenol, o-naphthylphenol, m-naphthylphenol, p-naphthylphenol, 2,5-di-t-butylphenol, 2,4-di-t-butylphenol, 3,5-di-t-butylphenol, 2,5-dicumylphenol, 3,5-dicumylphenol, p-cresol, etc. Of those monophenols, preferred are p-t-butylphenol, p-cumylphenol, p-phenylphenol, etc.
As the branching agent, for example, employable are compounds having at least three functional groups, such as 1,1,1-tris(4-hydroxyphenyl)ethane, xcex1, xcex1xe2x80x2, xcex1xe2x80x3-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene, 1-[xcex1-methyl-xcex1-(4xe2x80x2-hydroxyphenyl)ethyl]-4-[xcex1xe2x80x2, xcex1xe2x80x2-bis(4xe2x80x3-hydroxyphenyl)ethyl]benzene, phloroglucinol, trimellitic acid, isatinbis(o-cresol), etc.
In general, the polycarbonates for use in the invention preferably have a viscosity-average molecular weight of from 10,000 to 100,000, more preferably from 14,000 to 40,000.
[ii] Composite Rubbery Graft Copolymer (Component (B))
The composite rubbery graft copolymer of the component (B) is one as prepared by grafting a composite rubber with one or more vinyl monomers. Preferably, it is prepared by grafting a composite rubber, which has a structure composed of from 1 to 99% by weight of a polyorganosiloxane rubber component and from 1 to 99% by weight of a polyalkyl acrylate rubber components, the two components being so intertwisted with each other as not to separate from each other, and has a mean particle diameter of from 0.01 xcexcm to 0.6 xcexcm, with one or more vinyl monomers.
The composite rubbery graft copolymer may be produced in any known manner, for example, according to the methods described in JP-A64-79257 and 1-190746. For producing it, for example, a polyorganosiloxane rubber latex is first prepared, and monomers for polyalkyl (meth)acrylate rubbers are infiltrated into rubber particles in the polyorganosiloxane rubber latex, and then polymerized in the rubber particles.
The polyorganosiloxane rubber may be prepared by mixing a linear organosiloxane such as dimethylsiloxane or the like with from 0.1 to 30% by weight of a polyfunctional, silane-based crosslinking agent such as trimethoxymethylsilane, tetraethoxysilane or the like, and polymerizing them in emulsion.
For the latex production, usable is the method disclosed in U.S. Pat. No. 2,891,920. According to the method, the emulsion polymerization may be effected by mixing the components noted above in water, in the presence of a sulfonic acid-based emulsifier such as an alkylbenzenesulfonic acid, an alkylsulfonic acid or the like, which acts also as a polymerization initiator, for example, in a homogenizer.
The resulting polyorganosiloxane rubber latex is then neutralized with an aqueous alkali solution of sodium hydroxide or the like, to which are added an alkyl (meth)acrylate such as methyl acrylate, n-butylacrylate or the like, a crosslinking agent such as ethylene glycol dimethacrylate or the like, and a grafting reaction promoter such as allyl methacrylate or the like. In that condition, those additives are infiltrated into the polyorganosiloxane rubber particles. Next, an ordinary radical polymerization initiator is added thereto, and the monomers are polymerized to give a composite rubber latex in which the crosslinked polyalkyl (meth)acrylate rubber structure formed is intertwisted with the crosslinked polyorganosiloxane rubber structure so that the two rubber components are substantially unseparable.
To the composite rubber latex, added are vinyl monomers (e.g., alkenyl aromatic compounds such as styrene, etc.; methacrylates such as methyl methacrylate, etc.; acrylates such as methyl acrylate, etc.; vinyl cyanides such as acrylonitrile, etc.), and these are radical-polymerized in a single-stage or multi-stage polymerization manner. Then, calcium chloride or the like is added to the resulting latex for salting out to obtain the intended, composite rubbery graft copolymer through solidification and isolation.
[iii] Halogen-Free Phosphoric Ester (Component (C))
The halogen-free phosphoric ester of the component (C) for use in the invention does not contain a halogen atom such as bromine or the like. Therefore, the scrap of the moldings of the composition of the invention pollutes little the environment.
The halogen-free phosphoric ester includes, for example, monophosphates or polyphosphates of the following general formula (I): 
In formula (I), R1 to R4 each independently represent an optionally-substituted aryl group, and these may be the same or different; X represents an optionally-substituted arylene group; a, b, c and d each represent 0 or 1; and p represents an integer of from 0 to 5. Where two or more phosphates are used, as combined, p in formula (I) shall be the average of p in plural phosphates. The substituents for the aryl and arylene groups include, for example, an alkyl group having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 10 carbon atoms, an aryl group such as phenyl, tolyl, etc. The aryl and arylene groups may have one or more substituents.
Specific examples of the halogen-free phosphates of formula (I) include monophosphates such as triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tribiphenyl phosphate, etc.; and polyphosphates such as phenyl-resorcinol polyphosphate, phenyl-hydroquinone polyphosphate, phenyl-cresyl-resorcinol polyphosphate, phenyl-cresyl-hydroquinone polyphosphate, tetraphenyl-resorcinol diphosphate, tetraphenyl-hydroquinone diphosphate, phenyl-tricresyl-resorcinol diphosphate, phenyl-tricresyl-hydroquinone diphosphate, tetrabiphenyl-resorcinol diphosphate, tetrabiphenyl-hydroquinone diphosphate, etc. Of those, preferred are polyphosphates, as being effective for preventing the polycarbonate resin composition comprising them from adhering to molds and from soiling molds while the composition is thermally molded. One or more of these monophosphates and polyphosphates may be used either singly or as combined.
[iv] Polytetrafluoroethylene (Component (D))
Polytetrafluoroethylene (PTFE) of the component (D) is to prevent the polycarbonate resin composition comprising it from melting and dripping and to make the composition have good flame retardancy. Therefore, PTFE with good fibrillating ability is preferably used.
The fibrillating ability of PTFE is meant to indicate that PTFE could fibrillate after having received shear stress of plasticization while the composition comprising it is kneaded or molded through injection, and this brings about high flame retardancy of the moldings of the composition.
PTFE with such fibrillating ability for use in the invention is not specifically defined. For example, preferred are those that are grouped in Type 3 in the ASTM standard. As specific examples of commercially-available products of PTFE grouped in Type 3, mentioned are Teflon 6-J (trade name, from Mitsui-DuPont Fluorochemical), Polyflon TFE D-1 (trade name, from Daikin Industry), Polyflon TFE F-104 (trade name, from Daikin Industry), etc. As others not in Type 3 but are employable herein, for example, mentioned are Algoflon F5 (trade name, fromMontefluos), PolyflonMPA FA-110 and Polyflon TFE F201 (both trade names, from Daikin Industry), etc.
Two or more of those PTFEs maybe used, as combined. PTFEs with fibrillating ability such as those mentioned above may be prepared, for example, by polymerizing tetrafluoroethylene in an aqueous medium in the presence of sodium, potassium or ammonium peroxydisulfide, under a pressure falling between 1 and 100 psi and at a temperature falling between 0 and 200xc2x0 C., preferably between 20 and 100xc2x0 C.
(2) Proportions of Constituent Components
[i] Regarding the proportions of the polycarbonate resin (A) and the composite rubbery graft copolymer (B), the ratio by weight of (A) to (B) falls between 99:1and 90:10, but preferably between 99:1 and 92:8. With the proportion of the composite rubbery graft copolymer being at least 1 in terms of the ratio noted above, the moldings of the composition could have satisfactory impact resistance. However, if the proportion of the composite rubbery graft copolymer is larger than 10 in terms of that ratio, a large amount of the flame retardant must be added to the composition in order not to lower the flame retardancy of the composition. If so, the impact resistance of the moldings of the composition will lower. With the proportion of the polycarbonate resin being at least 90 in terms of the ratio noted above, the composition well exhibits the properties of polycarbonates.
[ii] Regarding the proportion of the halogen-free phosphoric ester of the component (C), the amount of the component (C) is from 0.3 to 1.2 parts by weight relative to 100 parts by weight of the sum total of the component (A) and the component (B). The component (C) exhibits a synergistic effect for improving the flowability of the composition, and is effective for preventing the moldings of the composition from having silver marks. If the amount of the component (C) is smaller than 0.3 parts by weight, the composition could not have satisfactory flame retardancy; and if larger than 1.2 parts by weight, the composition will lose the characteristics of polycarbonates, in particular, the impact resistance of the moldings of the composition will be poor. Therefore, adding the component (C) to the composition in an amount overstepping the defined range is unfavorable.
[iii] Regarding the proportion of the polytetrafluoroethylene of the component (D), the amount of the component (D) is from 0.01 to 1.0 part by weight relative to 100 parts by weight of the sum total of the component (A) and the component (B). If the amount of the component (D) is smaller than 0.01 parts by weight, the composition could not have satisfactory flame retardancy and its anti-dripping property will be poor. However, even if the amount of the component (D) is larger than 1.0 part by weight, such a large amount of the component (D) added could not produce any additional effect but is rather unfavorable in a sense of economy.
[iv] Regarding the relationship between the phosphorus content of the halogen-free phosphoric ester of the component (C) and the amount of the composite rubbery graft copolymer of the component (B), it is necessary that the ratio by weight of the amount of the composite rubbery graft copolymer (B) to the phosphorus content of the halogen-free phosphoric ester (C), or that is, [amount of the composite rubbery graft copolymer (B)/phosphorus content of the halogen-free phosphoric ester (C)] falls between 2 and 15. Within the defined range, the composition could have well-balanced physical properties. If the weight ratio is smaller than 2, the moldings of the composition could not have satisfactory impact resistance; and if larger than 15, they could not have satisfactory flame retardancy.
(3) The resin composition of the invention may optionally contain, in addition to the components (A), (B), (C) and (D) noted above, various inorganic fillers, additives and other synthetic resins, within the range not interfering with the object of the,invention.
For example, inorganic fillers may be added to the polycarbonate resin composition for the purpose of improving the mechanical strength and the durability of the composition. As specific examples of the inorganic fillers, mentioned are glass fibers, carbon fibers, glass beads, glass flakes, carbon flakes, carbon black, calcium sulfate, calcium carbonate, calcium silicate, titanium oxide, alumina, silica, asbestos, talc, clay, mica, quartz powder, etc. The additives include, for example, antioxidants such as hindered phenols, phosphorus compounds (phosphites, phosphates, etc.), amines, etc.; ultraviolet absorbents such as benzotriazoles, benzophenones, etc.; external lubricants such as aliphatic carboxylates, paraffins, silicone oils, polyethylene waxes, etc.; as well as mold-releasing agents, antistatic agents, colorants, etc. Other resins that may be added to the composition of the intention include, for example, polyethylenes, polypropylenes, polystyrenes, AS resins, ABS resins, polymethyl methacrylates, etc.
(4) Formulation and Kneading of Constituent Components, and Molding of the Resulting Composition
Formulation and kneading of the constituent components is not specifically defined, for which is employable any ordinary method. For example, employable are any of ribbon blenders, Henschel mixers, Banbury mixers, drum tumblers, single-screw extruders, double-screw extruders, co-kneaders, multi-screw extruders, etc. For kneading the components, the heating temperature may be any ordinary one, for example, falling between 240 and 340xc2x0 C.
The polycarbonate resin composition thus produced may be molded in various known molding methods of, for example, injection molding, blow molding, extrusion molding, compression molding, calender molding, rotary molding or the like. In particular, the composition is suitable to producing moldings in the fields of office automation equipment and electrical and electronic appliances, concretely, to producing housings of office automation equipment and electrical and electronic appliances such as notebook-type personal computers, etc., and battery packs of office automation equipment and mobile communication appliances such as portable telephones, cellular phone etc.